The Liberal Democrats have slumped to their lowest-ever poll rating in the wake of allegations that their former chief executive Lord Rennard sexually harassed female party activists.

For the first time in its monthly polls for The Independent, ComRes puts Nick Clegg’s party in fourth place behind the UK Independence Party. The Liberal Democrats are on just eight per cent, down two points on last month, while Ukip is on nine per cent (down one point).

The survey, taken between Friday and Sunday when the Rennard controversy dominated the headlines, suggests it has damaged the Liberal Democrats. It is a setback for Mr Clegg in the run-up to Thursday’s Eastleigh by-election caused by the resignation of Chris Huhne, the former minister who has admitted perverting the course of justice and awaits sentencing.

Liberal Democrat leader Nick Clegg has been forced to admit that his office knew for years of claims that a senior party figure might be sexually molesting volunteers and staff.

The Deputy Prime Minister changed tack in a statement on Sunday evening over the sex scandal which is engulfing his party.

He broke into the end of his holiday to admit for the first time that his office had been aware of the allegations surrounding his former chief executive Lord Rennard since 2008. But he said he was personally unaware of the claims.